A recent report in the journal Infection (Chean et al. 2012) describes rat bite fever in a patient with AIDS. I’ve written about rat bite fever before, and it’s not really a surprising case report. Streptobacillus moniliformis, the bug that causes the disease, is found in the mouths of most rats (and in the mouths of dogs more often than we’ve previously assumed). Rat bite fever is uncommon but far from rare, and this report focuses on the fact that it was in an AIDS patient. The case report itself isn’t too noteworthy since we know infection with S. moniliformis can happen even in healthy people, and someone with AIDS is going to be at increased risk of any type of infection.

However, there are a few interesting aspects to this particular case. The report described a 30-year-old AIDS patient who had a rather prolonged course of disease with fever, aches, diarrhea and weight loss, with subsequent development of joint pain and swelling. A large battery of tests didn’t identify the underlying cause. Eventually, "it was noted that he had two pet rats, one of which bit the man on his right index finger 1 month prior to presentation." That should have been a "eureka!’ moment for the physician. It doesn’t mean the disease was caused by the bite, but it made it clear that rat bite fever should be considered. The diagnosis was then made and the man received appropriate treatment.

While the clinical aspects of the case aren’t remarkable, there are some noteworthy points to consider:

  • It wasn’t until re-evaluation that it was discovered that the patient had rats and had been bitten. It’s quick and easy for a doctor to ask “Do you have pets or have you had contact with animals?” and in a case like this, it could have sped up the diagnosis and appropriate treatment.
  • The paper repeats the important statement that pet ownership rates among HIV/AIDS patients are similar to that of the general population. That’s also true for other groups at increased risk of infection.
  • They say “Physicians need to be cognisant of this [pet/human] relationship in order to prevent missing the diagnoses of zoonotic infections in their patients.” That’s a critical step. It’s easy to do. It’s not often done right.